1. Field of the Invention
The invention relates to a device for dewatering bulk or free-flowing input material by compression.
2. Description of the Background Art
Within system and process engineering, a starting material is generally processed during its successive treatment to the desired final product. As a general rule, this is done stepwise during its passage through different processing stations.
An example of such a type of processing is the workup of lignocellulose-containing material, such as wood, annual plants, straw, bagasse, and the like. In such processes, the processing stations of pre-grinding, washing, pre-steaming, dewatering, cooking, defibration, drying, and separation are passed through. The fibers obtained in this way can then be used to produce pulp in paper manufacturing or as wood fibers in the manufacturing of wood fiber production, for example of MDF products.
The invention is based on a device with which the input material is dewatered by compressing it. In the above-described process, such a device can, for example, be arranged as a plug screw in front of a cooker with the function of making possible the introduction of the free-flowing input material into a subsequently pressurized system with simultaneous dewatering of the input material.
The theoretical design of such a device provides a housing with a jacket pipe, in which a screw shaft with a circumferential helix rotates, which in cooperation with axially aligned feed strips transports the still loose input material to the opposite end of the jacket pipe. As a result of the jacket pipe tapering conically toward this end or the decreasing pitch of the screw helix, the input material is strongly compressed and the residual water present in the input material is squeezed out. The removal of the squeezed-out water takes place through openings in the jacket pipe, which are adapted in their size and shape to the type of input material.
In addition to the squeezing out of the residual water, the compression of the input material also serves to create a highly compressed material plug, which ensures sealing of the inlet opening against the pressurized cooker system.
One drawback of such devices results from the high compression of the input material, resulting in higher compression forces on the inside of the screw jacket. These cause high abrasion both on the screw helix and on the jacket pipe, so that known devices must be repaired or reinforced at regular intervals. The resulting shutdown times and work reduce the economical operation of such devices.
An additional drawback results from the fixed geometry of the elements involved in the dewatering, which makes adaptation of known devices to the uniqueness of varying input materials impossible.